1. Field of the Invention
The present invention relates to metal-oxide based memory devices.
2. Description of Related Art
One-time programmable (OTP) memory is used in integrated circuits for a variety of nonvolatile memory applications. OTP memory is typically implemented using charge storage, fuse, or anti-fuse techniques.
Anti-fuse type memory is programmed by applying a voltage pulse across a dielectric or other high resistance material to induce breakdown and form a low resistance current path through the material. Various materials including silicon oxide, silicon nitride, silicon-oxynitride, aluminum oxide, and hafnium oxide have been proposed for use in anti-fuse type memory. Typically programming voltages of 10 V or more are needed, which increases the complexity of circuitry for memory devices employing these types of materials. In addition, the breakdown process can take a relatively long time (for example greater than 1 microsecond) and require a large current, resulting in relatively slow programming speeds and high power consumption.
It is therefore desirable to provide high density anti-fuse type memory devices having relatively low programming voltages and fast programming times.